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Is there a relation between the camera's buffer and number of photographs which can be shot at a given fps? Let's say a camera can shoot 12 photos at 10fps. Then is it when the buffer is filled with 12 photos, the camera can't shoot anymore photos? Am I correct?
Then what's with the fps? Does it go with the processing power?

  • What problem are you trying to solve? – Michael C Mar 14 '16 at 21:05
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The buffer is a fast RAM of limited size. While it fills up with photos during a burst (or only after it's full in some implementations), the data is written to the storage card, which is much slower.
So the full published burst speed is only available while there's still space left in the buffer, once it is full, your burst speed will typically be constrained by the writing speed to the memory card.

This can depend on the card, but also on the I/O performance of the camera hardware, if you use a very fast card.

Of course, maximum burst speed can only be achieved with appropriate exposure settings, you can't very well shoot eg. 14fps with a shutter time of 1/10s.

So, to sum it up, if you want to shoot sustained bursts, buying a fast memory card can help to keep the fps up to a certain extent.

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Then is it when the buffer is filled with 12 photos, the camera can't shoot anymore photos? Am I correct?

Not quite. Many cameras may write some photos already before the moment of filling the buffer and burst will be longer. The speed of writing photos from buffer to the card indeed depends on the processing throughput. If camera writes photos to the card at least at the speed of capturing the burst is potentially unlimited.

Then what's with the fps? Does it go with the processing power?

FPS depends on following:

  • sensor read speed
  • shutter type
  • shutter curtain speed or shutter leaf speed or mirror speed (if any)
  • aperture mechanics responsiveness
  • exposure time
  • imposed limitations to make a camera more attractive than cheaper one
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    It is rarely an artificially imposed limitation other than the amount of memory given to the buffer. The shutter cycle time of cheaper cameras is usually longer because that allows a less robust (=cheaper) shutter mechanism to be used without failing prematurely. Even then, the slower, cheaper shutters are only rated for 50-100K actuations while the faster, more sophisticated and expensive shutter mechanisms are rated for life expectancies in the 300-400K range. The midgrade designs fall somewhere in between both in terms of cycling speed and longevity. – Michael C Mar 15 '16 at 5:00
  • @michael-clark: I do not have comprehensive clue in this sphere but I suppose that similar hardware may be used in a variety of cases to cut the costs.There are numerous examples of that camera mfgs do not even give same software for different models while they really could: Magic Lantern, the community-developed software, runs on a number of quite different Canon DSLRs. Another example: Nikon cuts customization options on cheaper models. – Euri Pinhollow Mar 15 '16 at 12:21
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    They've all got different shutter mechanisms. Some cameras in the lower tier may share a part #, but the xD and x0D models all have their own shutter design. Running ML on Canon cameras will not increase the burst rate. And ML must be adapted for each new model that comes out. Running an older version of ML will not work on a newer camera. ML may increase the buffer size and allow longer bursts, but the maximum frame rate will not change. – Michael C Mar 15 '16 at 20:35

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